The invention relates to a filter device comprising a filter candle for fastening and sealing filter fabrics and membrane tubes thereon, consisting of a central tube, around which a number of perforated support tubes is situated.
EP 0 066 921 describes a filter element for a pressure filter container of the type consisting of one central tube which is surrounded by a number of support tubes in order to support the filter fabric. A fastening of the filter fabric provided over the tubes is not described.
DE 89 03 445 U describes a simple filter candle for plastic melts, wherein a meshed filter means is slid, between a top part and a base part, over a perforated cylinder and is fastened by means of a clamping ring. The filter candle consists of a single tube. Backwashing is not provided.
DE 33 26 288 describes yet another filter candle for plastic melts. In this case, the sealing takes place by means of conical rings, due to the required high pressures of over 75 bar. In this case as well, neither cake discharge nor backwashing is provided. The known variants of the fastening of filter fabric hoses and membrane tubes on filter candles by means of screw-on clamps or strap clamps comprising radially protruding clamping devices consistently create difficulties with respect to cake discharge in filter candles or other devices in which filter candles are utilized.
Filter cake deposits onto the radially protruding clamping mechanisms, which results in the formation of a bridge between the individual filter candles and limits or even entirely prevents the cleaning of the filter candles.
Moreover, the strap clamps comprising protruding clamping mechanisms generally consist of materials having a greater strength and a lower material expansion coefficient than the material on which the filter fabric is fixed and sealed. During a cyclic temperature and pressure operation, this results in a loosening of the connection and, therefore, a functional failure of the filter candle(s). This is particularly disruptive, since, not only is there a loss of production, but repair must also be carried out.